The invention relates to a thermally protected case. It particularly relates to a case adapted to protect film during heat cycling in a parked car.
It is often desirable to keep a camera in an automobile. Cameras of the single use type may be stored in the car for unexpected picture taking opportunities such as accidents or other unexpected events. Further, point and shoot and SLR cameras are often carried in the car on vacations and for business purposes. The temperature inside a car parked in the sun may raise to quite high temperatures including temperatures of 180xc2x0 F. (82xc2x0 C.) and above. Long-term exposure to such temperatures is particularly common in the southwestern U.S., as well as other hot climates. Film is quite subject to deterioration at higher temperatures. Generally, film deterioration is quite rapid at temperatures above 160xc2x0 F. (70xc2x0 C.), and any lengthy exposure at temperatures above 130xc2x0 F. (55xc2x0 C.) may be harmful. The event is cumulative, meaning that the deterioration of film kept at high temperature or cycled to high temperatures becomes progressively worse with time.
When traveling in an automobile, it is often desirable to have a camera along for taking pictures. However, considerable inconvenience is often incurred in having to take the camera out of the car when parking to prevent the film from being ruined by high temperatures. It would be much more convenient to store the camera in the car, using a simple and inexpensive means to keep the camera and film cool.
The prior art contains several descriptions of methods to provide for cooling of a camera, using active techniques such as circulating air (U.S. Pat. No. 5,155,358) or water (U.S. Pat. No. 5,162,906). These systems are not practical for use in an automobile because of cost, complexity, and limited power available from the battery to run them for an extended period of time. A needed improvement would be a device which provides cooling without any active components, and which requires no external connections or power.
Many portable cooling devices have been disclosed, such as U.S. Pat. No. 4,322,954. All of these have required periodic replenishment of a consumable material such as ice or Freon. It is impractical and inconvenient to have to drain water from and add ice to a camera case. A needed improvement would be a device which does not use consumable materials.
The present invention uses encapsulated phase change material. It is well known to use such materials to provide heat, such as in heat packs used as hand warmers for people outdoors and medical skin warmers. U.S. Pat. Nos. 3,951,127; 4,077,390; and 4,872,442 describe such devices. These devices all use crystallization of material to provide heat, rather than the melting of the material to absorb it and maintain a lower than ambient temperature.
It would also be desirable if it was possible to store other materials in a closed automobile without their deterioration. Typical of such materials would be medical products that might be needed for an emergency or routine medical care which it is desirable to carry in the car. Other uses might be for storage of food products or sensitive electronic equipment.
A need exists to provide thermal protection for film, cameras, and other temperature sensitive materials stored inside an automobile. Film quality is significantly degraded by exposure to temperatures on the order of 130xc2x0 F. (55xc2x0 C.) or higher, while the temperature inside a car parked in the sun can reach over 200xc2x0 F. (95xc2x0 C.).
An object of the invention is to overcome disadvantages of prior methods of forming temperature sensitive materials.
Another object of the invention is the long-term storage of film in an automobile.
A further object of the invention is to provide low cost storage for temperature sensitive films.
These and other objects of the invention generally are accomplished by an article comprising photographic silver halide film substantially surrounded by a container comprising a phase change material, wherein said container will maintain said film at a temperature of below 130xc2x0 F. (55xc2x0 C.) when said container is repeatedly cycled over a 24-hour period reaching 180xc2x0 F. (82xc2x0 C.) for four hours.
In another embodiment of the invention, there is provided a container comprising an outer thermal insulating shell, a phase change material inside said shell wherein said container will maintain an internal temperature of less than 130xc2x0 F. (55xc2x0 C.) when cycled over a 24-hour period including up to four hours at 180xc2x0 F. (82xc2x0 C.).
The invention provides a low cost means to allow storage of heat sensitive materials in an automobile that is parked in the sun in the daytime and relatively cool at night.